1. Field of the Invention
The invention relates in general to an apparatus for protecting an integrated circuit and method thereof, and more particularly to an apparatus for protecting an integrated circuit, which can prevent the latch up of the integrated circuit by controlling the power input to the integrated circuit and method thereof.
2. Description of the Related Art
Referring to FIG. 1, a structural diagram of a conventional projector is shown. The conventional projector 100 includes a lamp 110, a lamp igniter 120, a microprocessor 130, and an integrated circuit 140. The lamp igniter 120 controlled by the microprocessor 130, uses an instant high voltage of 25,000 V approximately to ignite the lamp 110. Normally the integrated circuit 140 is an application specific integrated circuit (ASIC), which is controlled by the microprocessor 230 and performs various operations, such as driving the fan, under power on mode. The integrated circuit 140 receives power from the power source 150 via power source pins (not shown in the figure).
Normally, the projector 100 is at standby mode as switched on. Meanwhile, power of the power source 150 is inputted to the microprocessor 130 and the integrated circuit 140, the lamp igniter 120 has not ignited the lamp 110, neither has the integrated circuit 140 been driven to perform various operations. When the projector 100 enters the above-mentioned power on mode, the lamp igniter 120 will ignite the lamp 110, and the microprocessor 130 will send a signal instructing the integrated circuit 140 to perform normal operations. However, the instant high voltage required for igniting the lamp will generate a large amount of electromagnetic waves, which will easily enter the integrated circuit 140 via the power pins along with power output by the power source 150. Having a high voltage of 100 V approximately, the electromagnetic waves will reduce the impedance between the power pins of the integrated circuit and the ground level to be below 100 ohms, which is almost short-circuited, and causes the integrated circuit 140 to be latched up. After the integrated circuit 140 has been latched up, if the power source 150 still continues to supply power, the integrated circuit 140 will be penetrated and damaged by a large amount of currents accordingly.
In the prior art, a capacitance is installed at the power pins of the integrated circuit 140 to filter noises. However, the electromagnetic wave (100 V approximately) generated by the instant high voltage cannot be filtered without using a large amount of capacitance or a large capacitor, not only is it uneconomic but ineffective. Besides, an iron piece or a copper piece can be disposed on the peripheral of the integrated circuit to prevent the radiation of the electromagnetic waves. However, such mechanism has several limitations and has a complicated design.